1. Field of the Invention
The present invention relates to a roller-type one-way clutch used, for example, as a part for transmitting torque or as a back stopper in a driving apparatus of motor vehicles, industrial machines and the like.
2. Description of the Related Art
In general, a roller-type one-way clutch comprises an outer race, an inner race disposed coaxially with the outer race, a plurality of rollers disposed between an outer peripheral surface of the inner race and an inner peripheral cam surface of the outer race and adapted to transmit torque, and springs contacted with the rollers at an idle rotation side.
In the one-way clutch having such an arrangement, the inner race is rotated in only one direction with respect to the outer race by a cam mechanism constituted by the rollers and the cam surface. That is to say, it is designed so that the inner race is idly rotated with respect to the outer race in one direction and can transmit rotational torque to the outer race through the cam mechanism only in the other direction.
In general, in the roller-type one-way clutch, it is required to design so that, even if abrupt engagement is generated, all of the rollers must be engaged positively. For example, even under severe use conditions such as an environment where the clutch is exposed to high vibration and/or a very low temperature, in order to ensure the engaging ability of the roller-type one-way clutch, it is necessary to considerably increase an urging force (drag torque) of each of the springs for biasing the rollers toward the engaging direction. However, by doing so, there can arise problems regarding drag loss and wear during the idle rotation.
Further, in a roller type one-way clutch for motor bicycles, since the number of rollers is small (for example, three or six), if all of the rollers are not engaged positively, required design torque capacity may not be obtained.
As disclosed in Japanese Patent Application Laid-open No. 9-229096 (1997), the rollers are biased toward the engaging direction by the spring so that the rollers are engaged by the cam surface of the outer race. In this case, a number of springs corresponding to the number of rollers must be provided; however, in such a case, due to variation in properties of the springs, it was difficult to synchronize the rollers.